Scanning antenna having drive motors fixed with respect to the antenna



Sept. 22, 1970 R. JARRETT ET AL 3,530,477

SCANNING ANTENNA HAVING DRIVE MOTORS FIXED WITH RESPECT TO THE ANTENNAFiled March 25, 1968 '6 Sheets-Sheet 1 W gm fiddam v a ATTORNEYS.

Sfipf. 22, 1970 JARRETT ET AL 3 530,477

1 SCANNING AN NA ING DRIVE MOTORS FIXED WITH R ECT THE AN TENNA FiledMarch 25, 1968 3 Sheets-Sheet 2 ATTORNEYS Sept. 22, 1970 R. JARRETT ETAL SCANNING ANTENNA HAVING DRIVE MOTORS FIXED Filed March 25, 1968 WITHRESPECT TO THE ANTENNA Fla}. J

3 Sheets-Sheet 3 United States Patent 3,530,477 SCANNING ANTENNA HAVINGDRIVE MOTORS FIXED WITH RESPECT TO THE ANTENNA Richard Jarrett,Leigh-on-Sea, and Eric Davenport Gilbert, Chelmsford, England, assignorsto The Marconi Company Limited, London, England, a British compan FiledMar. 25, 1968, Ser. No. 715,607 Claims priority, application GreatBritain, Mar. 28, 1967, 14,053/ 67 Int. Cl. H01q 3/00 US. Cl. 343--765 4Claims ABSTRACT OF THE DISCLOSURE This invention relates to aerial drivemechanisms and particularly to such mechanisms for driving what areherein termed nodding scanning aerials, i.e. aerials which are requiredto move both in elevation andazimuth.

The invention is illustrated in and explained with reference to theaccompanying drawings in which FIG. 1 is an exploded diagrammatic viewof a known nodding scanning aerial arrangement, FIG. 2 is a diagrammaticview of one embodiment of the present invention, and FIG. 3 shows, to anenlarged scale, part of FIG. 2. Like references denote like parts in allfigures.

Referring to FIG. 1, 1 is an aerial which is mounted on trunnions 2which are pivoted in a support member 4, the pivotal axis beinghorizontal and indicated by the chain line 3. Movement about this axis 3is, of course, movement in elevation. Movement in azimuth is obtained bymovement about the axis indicated by the chain line 6, such movementbeing obtained by driving the support member 4 by a shaft 5 whichengages in a hole 8 in the support member 4. The axis 6 is, of course,the axis of the shaft 5 which is driven by a motor (not shown) installedin a fixed tower 7. The movement of the aerial 1 about the elevationaxis 3 is provided by a jack arrangement consisting of a screw 9connected by a trunnion at one end 10 to the aerial 1, and a nut member11 which is on the screw 9 and is rotatable through suitable reductiongear 12 by an elevation motor 13. As will be apparent when the nutmember is rotated by the motor the screw 9 is moved endwise and theaerial is moved in elevation.

This known arrangement has the disadvantage that because the mechanismdriven by the motor 13 and the motor itself are mounted on the movingsupport member 4, the total inertia associated with this member isincreased due to the extra weight of the motor and the mechanism. Thisis very undesirable. There is also the defect that fairly long flexibleleads must be used to supply electrical power to the motor 13. Inaddition lubrication and maintenance are made somewhat more icedifiicult by reason of the fact that the motor and mechanism are on amoving member.

The present invention seeks to avoid the above disadvantages.

According to this invention, in a nodding scanning aerial arragement ofthe kind in which an aerial is carried by a member which is pivotedabout one axis to a second member, said second member being in turnpivoted about a second axis perpendicular to the fixed member movementof said aerial about said one axis is obtained by a push-pull drivemember actuated by a motor driven shaft which, with its driving motor,is mounted on the fixed member and has its axis coincident with saidsecond axis.

Preferably the push-pull drive member is a screw shaft which is enteredinto a captive nut carried by and pivotally connected to the aerial,said screw shaft being rotated by said motor driven shaft through anepicyclic bevel drive comprising a bevel gear which is on the motordriven shaft and which drives through a ring gear having its axis atright angles to the motor shaft axis, a second bevel gear which is onthe screw shaft, said screw shaft being journalled in a member pivotedabout the axis of the ring gear.

Referring to FIGS. 2 and 3, the azimuthal drive for the aerial is as inFIG. 1 but the elevation drive is different. A captive nut member 11 isin effect pivotally connected to the aerial 1 by means of a clampingring member having radial ends 14 between which the nut 11 is pivoted asshown. Into the nut member 11 is entered a screwed shaft 9 which isdriven by the motor 13 by a drive mechanism best shown in FIG. 3. Thisdrive mechanism, and the motor 13, are both mounted on the fixed tower7.

Referring particularly to FIG. 3 the shaft 15 which is journalled in asupport bracket -19 fixed to the tower 7 rotated by the motor 13 (notshown in FIG. 3 but see FIG. 2). The axis of the shaft 5 is coincidentwith the azimuth axis 6 which intersects the elevation axis 3perpendicularly. On the end of shaft 15 is a bevel pinion wheel 16meshing with a ring bevel gear 17 the axis of which is at right anglesto and passes through the axis 6. The shaft of the ring gear 17 isjournalled in the ends of a fork or U member 20 in the cross piece ofwhich is journalled the screwed shaft 9. The member 20 can thus pivotabout the axis of the ring gear 17. The screwed shaft 9 is rotated by asecond bevel pinion 18 also meshing with the ring gear 17 as shown.

We claim:

1. An improved scanning aerial arrangement of the kind in which anaerial is carried by a member which is pivoted about one axis to asecond member, said second member is in turn pivoted about a second axisto a fixed member, said second axis being perpendicular to said oneaxis, means are provided for moving said aerial about said one axis, andmeans are provided for moving said aerial about said second axis; theimprovement comprising means for mounting a driving motor on said fixedmember; a motor driven shaft driven by said driving motor, said drivenshaft having its axis coaxial with said second axis; and a push-pulldrive member coupled to said driven shaft and said aerial for movingsaid aerial about said one axis.

2. An arrangement as claimed in claim 1 wherein the push-pull drivemember is a screw shaft which is entered into a captive nut carried byand pivotally connected to the aerial, said screw shaft being rotated bysaid motor driven shaft through an epicyclic bevel drive comprising abevel gear which is on the motor driven shaft and which drives through aring gear having its axis at right angles to the motor shaft axis, asecond bevel gear which is on the screw shaft, said screw shaft beingjournalled in a member pivoted about the axis of the ring gear.

3. An arrangement as claimed in claim 1, wherein the means for movingthe aerial about said second axis is mounted on said fixed member.

4. An arrangement as claimed in claim 1 wherein said push-pull dri-vemember is coupled to said drive shaft via gearing means mounted on saidfixed member.

4 References Cited FOREIGN PATENTS 8/ 1963 Great Britain.

ELI LIEBERMAN, Primary Examiner US. Cl. X.R.

